1. Field of the Invention
The present invention generally relates to an induction system for a multi-cylinder engine. More particularly, the present invention relates to an induction air pressure detection arrangement for an engine of an outboard motor.
2. Description of the Related Art
Outboard motors are used to power marine vehicles. The outboard motors typically include an engine positioned within a protective cowling of the outboard motor. The outboard motor is then attached to the back of the watercraft and used to propel the watercraft in a forward or reversed direction. The outboard motors include induction systems that supply air to a combustion chamber for combustion with fuel supplied by a fuel supply system.
The induction system can include a sensor that approximates the air pressure within a component of the induction system such as an auxiliary passage. The sensor also has been connected to a single component, such as a single intake pipe, of the engine to approximate the air pressure within the system as a whole.
During engine operation, however, air flow through the auxiliary passage increases to a high flow rate. Accordingly, accurately monitoring the pressure within the passage becomes difficult. The rapid passage of air results in often unresolvable errors in the detection system. Accordingly, the sensor can be moved to a different region of the induction system that has a larger diameter and which is closer to the combustion chamber.
A single sensor, therefore, has been positioned proximate a single combustion chamber. The single sensor can more accurately reflect the pressure of the portion of the induction system with which it is associated. The sensor, however, does not reflect the pressure of the balance of the induction system in a very accurate manner. For instance, where the single sensor is associated with the intake pipe of a single cylinder, the sensor may not provide an accurate reading when the particular cylinder is disabled or otherwise malfunctioning. In addition, the single sensor is particularly incapable of reading pressures for each intake pipe just prior to induction of an air charge into each combustion chamber from the associated intake pipe.